Apparatus for recovering anhydrous sodium sulphate and the like



yf 1939- H. w. DOENNECKE El AL 2,159,759

APPARATUS FOR RECOVERING ANHYDROUS SODIUM SULPHATB AND THE LIKE OriginalFiled Aug. 31, 1935 IN VEN TO R5 2 g? Ffzn y Wfloerme eke, 3 n; ///7////Ema yfl17ou3 C arll O, finds T'SOTL.

flTTORNEY Patented May 23, 1939 UNITED STATES PATENT OFFICE APPARATUSFOR RECOVERING ANHYDROUS SODIUM SULPHATE AND THE LIKE Company, Tulsa,Okla.,

ware

a corporation of Dela- Original application August 31, 1935, Serial N0.38,714. Divided and this application May 7,

1937, Serial No. 141,340

2 Claims.

This invention is directed to apparatus particularly adapted forrecovering anhydrous sodium sulphate in accordance with the methoddisclosed and claimed in United States Letters Patent 2,086,902, issuedtous July 13, 1937, of which this application is a division, saidapparatus, however, being equally well adapted for use in the recoveryof substances other than sodium sulphate and particularly those which,similarly thereto, have the characteristic of inverse" solubility abovea certain temperature. To enable those skilled in the art to comprehendand practise the present invention we shall therefore herein by way ofexample refer more particularly to its use in the recovery of anhydroussodium sulphate pursuant to our said method but not by way ofrestriction or limitation of its use therein or thereto.

Anhydrous sodium sulphate shall be considered as including any physicalform of the solid salt, sodium sulphate, which does not contain anycombined water of crystallization. It shall also be understood that thissalt may be of any degree of purity insofar as the sodium sulphatecontent is concerned, and that our apparatus may be utilized in thecommercial recovery of anhydrous sodium sulphate from water solutionscontaining only sodium sulphate or containing sodiumsulphate and otherconstituents or from "slurry consisting of a fluid mass having crystalsand/or particles of the hydrous Glaubers salt NazSO4.10I-I2O and of theanhydrous sodium sulphate in suspension therein. The recovery ofanhydrous sodium sulphate and like substances of inverse solubility fromnatural brine or other fluids by direct processes of various types hasheretofore been suggested but as far as we are aware none of these iscommercially practicable for the reasons, among others, that even whenrelatively concentrated solutions are available, their tendency todeposit scale on the walls and other parts of any apparatus in whichtheyare heated inhibits satisfactory recovery of the anhydrous salt or othersubstance on a commercial basis. Moreover, such scale adherestenaciously to the walls of the concentrating apparatus through whichheat exchange is effected and in such quantities as to rapidly impairthe efficiency of the apparatus and substantially prevent its continuousoperation by necessitating frequent shutdowns for the removal of thescale.

Our apparatus is therefore particularly useful in the commercialrecovery of anhydrous 'sodium sulphate by removal of water from a fluidor semi-fluid mass comprising water containing sodium sulphate inrelatively high concentration and thus either wholly or only partiallydissolved therein, and we may therefore utilize as materials from whichthe anhydrous salt is to be extracted either crystals of the hydroussalt, which melt at a relatively low temperature with a portion of thecontained sodium sulphate dissolving in the released water ofcrystallization, or slurry containing such crystals or crystals ofanhydrous sodium sulphate in suspension in a saturated solution of thesalt, or solutions, saturated or unsaturated, wherein the quantityrelationships of the contained constituents are such as to permitprecipitation of sodium sulphate by evaporation; alone. These materialsare obtainable readily from certain natural brines or other sources; forexample, the hydrous salt Na:SO4.l0HzO may be recovered with the aid ofthe method for the recovery of crystalline Glaubers salt disclosed inUnited States Letters Patent 2,007,956, issued July 16, 1935, to SidneyH. Davis, Carl 0. Anderson and Rudolph Stengl.

An object of our invention, therefore, is the provision of apparatusadapted for the continuous heating and agitation of the fluid from whichsodium sulphate or other material is to be extracted andevaporation ofcontained water therefrom without adherence or caking of the solid onthe walls and/or other portions of apparatus contacted by the fluid.

A further object ,is the provision of an improved mechanism for thecombustion of gas and air beneath the surface of a fluid whereby directheating of a salt bearing solution may be eil'ected and its containedwater rapidly and economically evaporated with resultant commercialrecovery of the material dissolved therein.

'A still further object of the invention is the provision of a novelburner adapted for the submerged combustion of fuel beneath the surfaceof a fluid and substantially out of contact therewith.

Other objects, purposes and advantages of the invention will hereinaftermore fully appear or will be understood from the following descriptionof apparatus constructed in accordance therewith of which a preferredembodiment is shown in the accompanying drawing.

In said drawing, Fig. 1 is a somewhat diagrammatic side elevation ofsaid apparatus partially in vertical section, and

Fig. 2 is an enlarged detail of an improved burner constructed inaccordance with the invention.

The same characters are used to designate the same parts in bothflgures.

The apparatus may comprise a tank T desirably made of Monel metal orother relatively noncorrosive substance and desirably provided with asmooth interior finish; its side walls I preferably converge near thebottom into an elongated relatively narrow U-shaped trough 2 withinwhich is disposed a screw conveyor 3 of a usual type operated by anyconvenient means (not shown) and adapted for conveying to a suitablepoint in the trough for removal the solids precipitated from thesolution. These precipitated solids, gathered together. at such point bythe conveyor, are in the form of relatively small particles and may thusbe removed with the aid of any suitable apparatus no speciflcdescription or illustration of which is required.

The tank is conveniently supported to extend below the floor level Ffrom suitable legs 5 of a frame comprising also horizontal retainingbars 0, and the upper edges of the tank are outwardly flanged at I torest upon the uppermost set 8' of these bars.

The tank may be of any desired form, preferably an elongated oval inhorizontal section, and of any convenient length; for example itslength, measured parallel to the conveyor axis, may be about twice itswidth, measured transversely thereof. and with such a tankwe may utilizeone or more of our novel burners. Thus, with a tank T as shown in Fig.1, we provide the submersible burner B. hereafter more fully described,which is desirably dis osed at about the center of the tank: if morethan one burner is provided they will preferably be positioned atsuitable intervals in its longitudinal central plane. The burner B isprovided with any suitable fuel and air mixture throu h a verticallymovable supporting pipe ID. the upper end of which is received in onebranch of a T-fltting i2: a flexible conduit l3 leads from the latter toa valve ll interconnected with the outlet port of a mixing chamber ll. A

valve controlled air supply pine l1 and a similarly controlled gassupply pipe I8 are connected into the mixing chamber is so that bymanipulation of the several valves 9. combustiblemixture of fuel and airmay be fed to the burner and the proportion of fuel to air as well asthe quantity of the mixture delivered readily regulated in accordancewith desired operating conditions.

The T-fitting l2 from which the burner is suspended also supports aslide rod which extends upwardly therefrom. This rod may consist of asmall pipe attached to the fitting through the medium of a sleeve 2|.and the upper end of the pipe is closed by a cap 22 to prevent escape.of fuel. The rod 20 is vertically slidable in a sleeve 23 supported bybrackets 23' from horizontal bars 24 or any other convenient supportingmeans positioned above the tank and thereby permits vertical movement ofthe burner relatively to the tank when and as desired.

A counterweight 25 is preferably connected to a lug 26 on the r-flttingl2 through the medium of a flexible cord or chain 21 running over asheave 20 to substantially counterbalance or slightly overbalance theburner, guide rod and parts rigidly connected thereto to facilitateraising the burner from the tank and lowering it thereinto, and toreleasably hold it in lowered position we provide movable latches 30carried by a cross bar 3| on top of the tank and adapted to engage theflange 32 of a collar 33 adJustably secured to the burner supply pipeIII by means of a set screw 3|.

The burner B which may desirably be formed principally of steel or anyother suitable metal, comprises a cylindrical tube 35 threaded to supplypipe and serving as an inlet port and to support other portions of theburner therefrom. An outwardly flaring conical portion 36 is welded orotherwise permanently united to tube 35, and a larger cylindrical tube31 forming the burner combustion chamber is similarly united with theouter edge of the conical portion 36. Within the chamber just below thejunction of these parts a pair of wire screens may be secured bysoldering, brazing or the like, the screens being slightly spaced apartand of sufliciently flne mesh to serve as flame guards againstpropagation of flame in the conical portion 36 or supply pipe i0 whenthe combustible mixture fed to the burner through the latter is burnedin the combustion chamber 31.

In the performance of the method disclosed and claimed in our saidLetters Patent with the aid of the apparatus just described, latches 30are released and the burner is raised from the tank sufllciently for thelower end of its combustion chamber to clear the level L of the fluidand preferably to clear the floor level F. The several control valvesare next operated to supply a mixture of fuel and air in suitableproportions and quantities and the burner is then lighted. Uponthereafter being lowered into the fluid, the pressure of the gas and airmixture in the burner is suflicient to overcome the opposing pressure ofthe fluid in the tank, so that as the burner is submerged the productsof combustion escape from its lower end and rise through the fluid,causing violent agitation thereof.

By the provision of a combustion chamber of uniform diameter throughoutand thus devoid of any restriction or narrowing at the point of egressfrom the burner of combustion products, we obtain highly efliclentheating of the fluid and larger burner capacity than is the case insubmerged burners having restricted outlets for the combustion products.Thus, a burner having a combustion chamber 6 inches in diameter has beenoperated at an hourly consumption of 900 cu. ft. of natural gas withwhich sufllcient air was premixed to insure complete combustion, withconsequent release of heat at the rate of approximately 900,000 13. t.u. per hour. It will be understood, however, the maximum limit of thecapacity of a burner of this size may be considerably higher witheiflcient and economical release of heat at a more rapid rate, theresults obtained during one period of normal operation having hereinbeen cited for purposes of example only.

In our burner the total absence of restriction in the combustionchamber, particularly at its lower or outlet end, also causes theescaping combustion products to effect extremely active agitation of thefluid in which the burner is submerged which asslsts in minimizingincrustation of the exterior surfaces of the burner by scale depositedfrom the fluid.

As a general rule we prefer to construct the burner in such manner thatthe ratio of the length to the inner diameter of the combustion chamberis approximately 5:1, and when approximately this ratio is observedcertain other advantages are realized which are not obtainable to a likeextent in similar burners the corresponding dimensions of which departmaterially from this ratio. Thus. as is well known, initial introductionof a lighted submersible burner into a fluid sets up violent agitationof the fluid and causes considerable bumping or churning therein, butwith our burner this action is of but short duration, after which theaction of the fluid changes to a fairly uniform but still vigorousebullition due to the buoyancy of the products of combustion which aresubstantially uniformly and regularly discharged into it from thecombustion chamber outlet of the burner and at a substantially uniformpressure.

The walls of the combustion chamber, which are composed entirely ofsteel or other suitable metal, form a confining yet heat conductiveenvelop for the gases within which substantially all combustion takesplace and are thus maintained in close proximity to an area of intenseheat extending from the outlet end of the chamber almost to its inletend and when this area is of considerable length, as in a burner havingthe dimension ratio just mentioned, complete combustion of the gas, evenwhen introduced to the burner at high velocity and in large volume, may

-be readily obtained, without, however. material impairment of heattransfer to the fluid either through sudden rapid expansion of thegaseous combustion products or material delay in effecting their contactwith the fluid after completion of combustion in or Just below the endof the burner.

Some reference has been made to the pressure of the combustible mixturesupplied to the bumer and to its depth of submersion and it will beunderstood that these factors may be regulated in accordance withpreference and may require some modification under various specificoperatin: conditions. However, certain general principles may desirablybe observed in relation thereto, for example. higher fuel and airpressures up to perhaps lbs. gauge are usually to be preferred whenrelatively small burners are employed, since such pressures effectivelyminimize the deposition of scale on the exterior of the burner andmaintain active agitation of the solution. With larger burners, however.these pressures may be reduced to points just suflicient toinsuremaintenance of continuous combustion in the burner and escape ofits products therefrom at the depth of submergence desired, and withthis qualification, changes in the latter depth within reasonable limitsappear to have but relatively slight effect upon the operatingefl'lciency of the burner, although we prefer to operate the 6-inchburner herein described with its outlet end submerged to a depth ofapproximately 3 ft. below the level of the fluid in the tank.

In the operation of the burner in the manner herein mentioned, transferof heat to the fluid isefiected by transmission through the burner walland also directly by contact of the products of combustion and a highdegree of efficiency is thereby obtained with the result that containedwater is rapidly evaporated and, when the fluid is a slurry or solutionof Glaubers salt, anhydrous sodium sulphate is precipitated to thebottom of the tank for removal therefrom. Moreover, thecontinuous'relatively violent agitation of the fluid causes theparticles of the precipitate to grow to appreciable size before theirultimate deposition at the bottom of the tank whereby handling and/orother operations into which they subsequently enter are facilitated, andby regulation of the degree of agitation by means of the burnercontrolling valves and by adjustment of the depth of submergence, thesize of the particles may be subjected to limited control.

At the initiation of the dehydration process, the tank T is supplied tothe desired level with Giauber's salt, slurry or other material fromwhich dehydrated salt is to be extracted. The burner, maintained inelevated position and thus out of contact with the fluid, is thenlighted and its control valves manipulated so as to supply it withdesired quantities of a suitable mixture of fuel and air, and thelighted burner is then slowly lowered into the fluid. When it hasreached the proper depth in the tank, corresponding to that for whichflanged collar 33 has previously been set on supply pipe ill, the burnerand its associated mechanism are locked in position by manipulation ofthe latches and thereafter continue to operate for any desired period.The screw conveyor in the bottom of the tank may then be set in motionto carry the precipitated material to a convenient point for removalfrom the tank and upon its removal and drying in any convenient way itis ready for use.

In the course of the operation of the burner the products of combustionand water vapor are given off in considerable quantities and may beremoved from the vicinity of the apparatus by means of a suitable shieldand conduit or other ventilating apparatus (not shown). The reduction ofthe water content of the fluid in the tank together with the extractionand removal of the precipitate, usually'carrying with it smallquantities of the solution, causes substantially continuous materialdepletion of the total volume of fluid in the tank, and to maintain thisvolume substantially constant for continuous operation the solutioncarried with the removed material may be recovered therefrom as bycentrifuging and returned to the tank along with fresh solution, slurryor the like, which may be supplied either continuously or intermittentlyas desired. Substantially continuous extraction may thus be maintainedfor relatively long periods without the usual caking and/or cloggingoccurring from time to time in apparatus heretofore constructed andoperated in accordance with known methods. and interruption of theoperation of our apparatus for such causes is therefore substantiallyunnecessary. Moreover, the walls of our fluid tank are heated onlyindirectly by contact of the heated solution therewith and are not, asin apparatus heretofore known, heated to a temperature greater than thatof the solution and this, together with the violent agitation of thesolution which may readily be maintained in the tank when our burner isemployed and operated as herein described prevents adherence ofprecipitated solids to the tank walls, burner and associated parts.

While we have herein described our invention with considerableparticularity, referring more especially to its use in evaporationrecovery of anhydrous sodium sulphate in a commercial way in accordancewith the method of our said Let-' ters Patent 2,086,902, it will beunderstood our apparatus is eminently suitable for performance of othermethods involving submerged combustion and that changes andmodifications in the form, construction and arrangement of the severalparts will readily occur to those skilled in the art and may be made ifdesired without departing from the spirit and scope of the invention asdefined in the appended claims.

Having thus described our invention, we claim and desire to protect byLetters Patent of the United States:

1. A burner for the submerged combustion of fuel beneath the surface offluid and substantially out of contact therewith comprising a hollowapproximately cylindrical metal tube of interiorly unobstructed uniformcross sectional area from end to end forming a downwardly directedcombustion chamber for confining the products of combustion and havingthe sole outlet therefor at its lower end of like cross sectional area,a hollow metal portion forming a frusto-conical expansion chamber havingits lower end co-extensive and integrally united with the upper end ofsaid tube, and means secured to the upper end of said portion forintroducing axially into the expansion chamber a combustible mixture offuel and air under pressure in a downwardly directed stream and forsupporting said portion and tube beneath the surface of the fluid inheat exchange relation therewith.

2. A burner for the submerged combustion of fuel beneath the surface offluid and substantially out of contact therewith comprising a hollowapproximately cylindrical tube formed of heat conductive materialdefining a combustion chamber and adapted to conduct heat derived fromthe combustion of gaseous fuel therein to the surrounding fluid bycontact of its exterior surface therewith, said tube having anunobstructed opening at its lower end transversely co-extensive withsaid combustion chamber and forming the sole outlet for passage ofcombustion products from said chamber into the fluid, means integralwith the upper end of said tube providing a frusto-conical expansionchamber having a downwardly divergent boundary transversely co-extensivewith said combustion chamber at its lower end, and means for introducinginto said expansion chamber a downwardly directed stream of fuel andairin combustible mixture.

HENRY W. DOENNECKE.

